我有一个包含 16 个 JMenuItems 的 JMenu,我希望预先显示 3 个项目,其余 13 个项目以 500 毫秒的延迟淡入。有没有办法在 Java 中制作这个动画?
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2 回答
4
这并不像听起来那么容易。
基本上,我最初认为“我将在弹出菜单中附加一个弹出侦听器,菜单项被添加到”......但显然这不太好用。菜单弹出是根据需要动态构建的。有道理,但还是很痛苦。
所以相反,我发现如果我等待,addNotify
我可以简单地启动动画引擎。
动画引擎是一个简单的概念。它有一个javax.swing.Timer
以固定间隔滴答作响。再加上开始时间和持续时间,我们就可以计算出动画的进度,并alpha
根据需要生成值。
剩下的唯一一件事就是通知所有相关方动画已更改,瞧……
import java.awt.AlphaComposite;
import java.awt.BorderLayout;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.NumberFormat;
import java.util.ArrayList;
import java.util.List;
import javax.swing.JFrame;
import javax.swing.JMenu;
import javax.swing.JMenuBar;
import javax.swing.JMenuItem;
import javax.swing.JPanel;
import javax.swing.JPopupMenu;
import javax.swing.Timer;
import javax.swing.UIManager;
import javax.swing.UnsupportedLookAndFeelException;
import javax.swing.event.PopupMenuEvent;
import javax.swing.event.PopupMenuListener;
public class FadeMenu {
private AnimationEngine engine;
public static void main(String[] args) {
new FadeMenu();
}
public FadeMenu() {
EventQueue.invokeLater(new Runnable() {
@Override
public void run() {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
} catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {
}
engine = new AnimationEngine();
JMenuBar mb = new JMenuBar();
JMenu flip = new JMenu("Flip");
flip.add("Static 1");
flip.add("Static 2");
flip.add("Static 3");
flip.add(new FadeMenuItem("Fade 1"));
flip.add(new FadeMenuItem("Fade 2"));
flip.add(new FadeMenuItem("Fade 3"));
flip.add(new FadeMenuItem("Fade 4"));
mb.add(flip);
JFrame frame = new JFrame("Testing");
frame.setJMenuBar(mb);
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setLayout(new BorderLayout());
frame.add(new TestPane());
frame.pack();
frame.setLocationRelativeTo(null);
frame.setVisible(true);
}
});
}
public class TestPane extends JPanel {
public TestPane() {
}
@Override
public Dimension getPreferredSize() {
return new Dimension(200, 200);
}
}
public class FadeMenuItem extends JMenuItem {
public FadeMenuItem(String text) {
super(text);
engine.addTimingListener(new TimingListener() {
@Override
public void timingEvent() {
repaint();
}
});
}
@Override
protected void paintComponent(Graphics g) {
Graphics2D g2d = (Graphics2D) g.create();
g2d.setComposite(AlphaComposite.SrcOver.derive(engine.getAlpha()));
super.paintComponent(g2d);
g2d.dispose();
}
@Override
public void removeNotify() {
Container parent = getParent();
if (parent instanceof JPopupMenu) {
JPopupMenu menu = (JPopupMenu) parent;
engine.stop();
}
super.removeNotify();
}
@Override
public void addNotify() {
super.addNotify();
Container parent = getParent();
if (parent instanceof JPopupMenu) {
JPopupMenu menu = (JPopupMenu) parent;
engine.restart();
}
}
}
public interface TimingListener {
public void timingEvent();
}
public class AnimationEngine {
private Timer fade;
private float alpha;
private long startTime;
private long duration = 1000;
private List<TimingListener> listeners;
public AnimationEngine() {
listeners = new ArrayList<>(5);
fade = new Timer(40, new ActionListener() {
@Override
public void actionPerformed(ActionEvent e) {
long elapsed = System.currentTimeMillis() - startTime;
if (elapsed >= duration) {
((Timer) e.getSource()).stop();
alpha = 1f;
} else {
alpha = (float) elapsed / (float) duration;
}
fireTimingEvent();
}
});
fade.setRepeats(true);
fade.setCoalesce(true);
fade.setInitialDelay(500);
}
public void addTimingListener(TimingListener listener) {
listeners.add(listener);
}
public void removeTimingListener(TimingListener listener) {
listeners.add(listener);
}
protected void fireTimingEvent() {
for (TimingListener listener : listeners) {
listener.timingEvent();
}
}
public void restart() {
fade.stop();
alpha = 0;
fireTimingEvent();
startTime = System.currentTimeMillis();
fade.start();
}
public float getAlpha() {
return alpha;
}
public void stop() {
fade.stop();
}
}
}
虽然这适用于 Windows,但我担心它可能不适用于其他平台,因为生成菜单的方式(部分)由 UI 委托控制。这可能会变得非常混乱,很快
于 2013-04-09T03:35:06.337 回答
0
启动计时器以触发事件以淡入
于 2013-04-09T03:19:14.930 回答